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<p>Our overarching objective is to elucidate the mechanism(s) governing the uptake of pharmaceuticals from water and soil by vegetables. This knowledge will facilitate the development of best management practices to mitigate the accumulation of CECs in vegetable fresh produce. The proposed project directly addresses nphysical or molecular mechanisms that allow foodborne hazards of pharmaceuticals to internalize into fresh produce. Consumption of pharmaceutical-tainted fresh produce, especially raw vegetables, represents a direct route of human exposure to CECs. The trace levels of pharmaceutical mixtures in fresh vegetable produce might adversely affect human health. Moreover, antibiotics (one major class of pharmaceuticals proposed for study) could exert selective pressure on native antibiotic resistant populations of bacteria in human and animal gastrointestinal tracks hence accelerating the development and proliferation of antibiotic resistance. Reducing uptake of CECs by vegetables during agricultural production is a key step in improving food safety. Surely, reduced uptake by vegetables reduces human exposure to pharmaceuticals in natural environments. Little is known about the mechanism of pharmaceuticals movement into vegetables from soil and water. Here, our central hypothesis is that water flow in soils and vegetables is the major process by which pharmaceuticals translocate from soil and water to vegetables. The accumulation of pharmaceuticals depends on vegetable types, plant tissue constituents and growth condition, physicochemical properties of CECs, and soil properties. Mitigating uptake of CECs by vegetables could be achieved by reducing CEC concentrations in soil water flowing into vegetables.</p><p> To test this hypothesis, and to achieve our overall research goals, we propose the following four specific aims:</p><p><ol><li> Quantify and rank the uptake of multiple representative human and veterinary pharmaceuticals by selected vegetables (carrot, celery, cucumber and lettuce).</li><li> Evaluate which vegetable organs (roots, leaves etc.) and growth factors most significantly influence the rate and magnitude of pharmaceutical uptake and accumulation in vegetables.</li><li> Assess the influence of pharmaceutical sorption/desorption by soils on their uptake via vegetable roots</li><li> Discover and investigate novel soil management and irrigation practices that minimize pharmaceutical accumulation in vegetables. </li></ol></p>
Background. Consumption of pharmaceutical-tainted fresh produce, especially raw vegetables, represents a direct route of human exposure to chemicals of emerging concern (CECs). The major sources for human and veterinary pharmaceuticals that accumulated in vegetables can be tracked to the agricultural lands and irrigation water containing CECs. Land application of biosolids derived from livestock manures and sewage sludges, and agricultural irrigation with reclaimed water, are the major practice responsible for the accumulation of pharmaceuticals in fresh produce including vegetables. Although the pharmaceuticals typically found in fresh produce are usually below acceptable levels for daily intake, consumption of agricultural produce containing antibiotics could plausibly increase the populations of antibiotic resistant bacteria in the intestinal tracks of human and animals. Mitigating the accumulation of antibiotics in fresh produce during agricultural production is a crucial first step in improving food safety, which surely reduces human exposure to antibiotics. However, currently it is unclear how pharmaceuticals move into vegetables during growth, and the extent to which they accumulate. A better understanding the mechanism of vegetable uptake and accumulation of pharmaceuticals from soil and water will enable the development of scientifically-informed management practice that can help vegetable producers ensure food safety by minimizing or eliminating pharmaceuticals in fresh produce. Overall Hypothesis. The overarching objective is to elucidate the mechanism of pharmaceutical uptake by vegetables growing in water-soil systems. We hypothesize that pharmaceutical translocation to vegetables is controlled water flow in both soils and plants. Pharmaceutical accumulation depends on vegetable type, interaction of pharmaceuticals with plant tissue constituents, and the growth conditions. Specific Aims. (1) Screen and rank the uptake of multiple representative human and veterinary pharmaceuticals by selected vegetables (carrot, celery, cucumber and lettuce). (2) Evaluate sorption by vegetables and growth factors influencing the rate and magnitude of pharmaceutical uptake and accumulation in vegetables. (3) Assess the influence of pharmaceutical sorption/desorption in soils on the uptake by vegetable roots. (4) Investigate novel soil management and irrigation practices designed to minimize pharmaceutical accumulation in vegetables. Approaches. Vegetable uptake of representative pharmaceuticals will be investigated using both hydroponic and soil-pot experiments. Pharmaceuticals in plant tissues, soil and water will be extracted and quantitated by LC-MS/MS using the methods developed and used in our laboratory. The kinetics and magnitude of pharmaceutical uptake will be measured, and related to physicochemical properties of the pharmaceuticals, sorption by plant constituents, and with water flow in both soils and vegetables. In the pot experiments soils with different sorptive constituents (e.g. organic matter, clays) and textures will be used to delineate the role of sorption and water flow in influencing pharmaceutical accumulation in vegetables. Potential Impact and Expected Outcomes. New fundamental understanding is needed for mitigating uptake and accumulation of pharmaceuticals in fresh produce and vegetables. The results from this research project will be published in peer-reviewed journals, presented at conferences and outreach events in order to effectively transfer the knowledge to scientific communities, food producers, industries, policy makers, and the general public. Such knowledge helps guide vegetable producers to develop scientifically informed management practices that ensure food safety during the production phase, and ultimately to minimize chemical hazards in the fresh produce delivered to the public.